Inkjet printing recording material

ABSTRACT

A novel recording material for the inkjet printing process has a substrate and an ink receiving layer which is applied on at least one side of the substrate, the ink receiving layer containing an inorganic pigment and an ink fixative comprising at least two substances. The first substance is a polyamine epichorohydrin and the second substance is a polyvalent metal salt. This recording material is characterized in that the first substance is a medium-molecular, branched polyamine epichlorohydrin condensation product, the ratio of the first substance to the second substance is between 3:1 and 16:1, the pigment makes up at least 80 percent by weight with a D 50  particle size (Malvern) ranging from 4 μm inclusive to 12 μm inclusive, and the ratio of ink fixative to pigment ranges from 1:2 inclusive to 1:6 inclusive. The invention is further directed to a method for recording by the discontinuous inkjet printing process which uses the novel recording material.

PRIORITY CLAIM

This is a U.S. national stage of application No. PCT/EP02/09391, filedon 22 Aug. 2002. Priority is claimed on that application and on thefollowing application(s): Country: Germany, Application No.: 101 40677.0, Filed: 24 Aug. 2001.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed to a recording material for the inkjetprinting process having a substrate and an ink receiving layer which isapplied on at least one side of the substrate, the ink receiving layercontaining an inorganic pigment and an ink fixative comprising at leasttwo substances, the first substance being a polyamine epichlorohydrinand the second substance being a polyvalent metal salt. The invention isfurther directed to a process for recording by discontinuous inkjetprinting which uses the novel recording material.

2. Description of the Prior Art

Reaction products which are produced on the basis of amine compounds andepihalohydrins as auxiliaries for the ink receiving layers of inkjetrecording materials are known. In order to improve the water fastness ofprinted images which are generated by means of inkjet printers and whichshould be distinguished by excellent printing quality, JP-A-11 277 888,for example, proposes an auxiliary with a linear cationic resin that isformed as reaction product of an amine component containing a secondaryamine and another amine component containing at least two amino groupsand an epihalohydrin.

JP-A-11 277 887 is likewise directed to an auxiliary which increaseswater fastness and which has a structural formula of the linear cationicresin that is different than that in the above-cited reference and has acomparable effect. According to the description, however, thisstructural formula is expanded in order to reduce ink bleeding in imagesprinted by inkjet printers. In both of the references cited above, theindicated viscosity of the respective 20-percent aqueous solutionscontaining the proposed auxiliary is between 50 and 500 m Pa*s (B-type;30° C.).

JP-A-10 152 544 has the object of providing an inkjet recording paperwhich allows only slight ink bleeding in printed images generated byaqueous inks and, beyond this, enables a high color concentration andexcellent water fastness of the printed images. This object is supposedto be met through an addition to the coating compound in the form of abranched cationic resin presenting a reaction product of ammonia and atleast one, preferably primary, secondary or tertiary amine and anepihalohydrin. Further, preferable amines are polyalkylene polyamine andalkanolamine. The Brookfield viscosity of the 10-percent aqueoussolution of this cationic resin is 1 to 30 m Pa*s (60 rpm/25° C.).

With the aim of providing a production process for inkjet recordingpapers which has only low bleeding of ink droplets of aqueous ink andwhich enables printed images with high color density and excellent waterfastness, JP-A-09 240 139 proposes application of a branched cationicresin which is formed as a reaction product of a polyalkylene polyamineand an epihalohydrin and further, as the case may be, with an aliphaticamine component. The Brookfield viscosity of a 10-percent aqueoussolution containing the proposed cationic resin is indicated as 30 mPa*s (60 rpm/25).

The teaching to be gathered from the texts cited above is the suitableselection of the cationic resins to be used as auxiliaries inmedium-molecular linear form or low-molecular branched form. However,these texts do not indicate possible quantity ratios of the cationicresins to the pigments present in the ink receiving layers, nor do theyindicate that it is advantageous to combine the cationic resins to beused as auxiliaries with metal salts to obtain improved characteristicsfor recording materials to be used in inkjet printing methods.

A polyamide polyamine epichlorohydrin as ink fixative in the inkreceiving layer of an inkjet recording material is known from JP-A-09099 630. However, neither its precise structure nor its molecular weightis disclosed. Amorphous silicon dioxide is proposed as pigment; itsparticle size is indicated only in a very general way as averaging inthe range of 6 to 13 μm.

According to EP-A-0 914 962, outstanding inkjet recordingcharacteristics and superior printability in offset printing areachieved in a recording material due to its surface being especiallywell bonded; further, this recording material is distinguished by a highdegree of water fastness. It is stated in this text that this goal isachieved by a linear cationic resin in the ink receiving layer.Dimethylamine epichlorohydrin polycondensation products, among others,are mentioned as examples of this cationic resin. In addition to thecationic resin, the ink receiving layer further contains binders and, asthe case may be, pigments. The text does not indicate any advantageouscharacteristics of the pigments in the ink receiving layer. Also, thedescription in this text does not disclose any teaching regarding themixture ratio of ink fixative to pigment. A ratio of 1:10 is disclosedby way of example, while other examples disclose pigment-free inkreceiving layers.

Finally, EP-A-0 602 326 discloses a quaternary salt of a lineardimethylamine epichlorohydrin adduct with a degree of polymerizationbetween 2 and 2000 as ink fixative in the recording layer of an inkjetrecording paper. In addition to improved ink fixing, color distortion isprevented in the applied printed images through combination with a(meth)acrylamide diallylamine copolymer. Insofar as they are used at allin the recording layers disclosed in this text, inorganic and organicpigments considered to be suitable are those having a particle size inthe range of 4 μm. There is no indication in the text about theadvantageous combination of the dimethylamine epichlorohydrin adductwith polyvalent metal salts as ink fixative.

Also, the use of divalent or polyvalent metal salts in the recordinglayer of inkjet recording materials is known and is proposed withoutcombining with other agents improving ink fixing in DE-A-25 33 957 andDE-A-24 01 866, for example. However, using metal salts alone orpredominantly as ink fixatives in inkjet recording layers has thefundamental disadvantage that a true-color reproduction of applied inkprint images is rarely achieved.

EP-A-1 01 016 545 discloses a recording material for inkjet printing inwhich a mat finish, greater ink absorption, image quality,water-tightness, light fastness and ink transfer, as well as resistanceto ink bleeding, are to be achieved by means of a binder mixture for theimage receiving layer containing polyethylene glycol and polyvinylalcohol in a defined ratio. The image receiving layer can containpolyvalent metal salts and a compound from the group of polymericquaternary ammonium compounds or base polymers such aspoly(dimethylaminoethyl) methacrylate, polyalkylene polyamine andcondensation products thereof with dicyanodiamide andamino-epichlorohydrin polycondensates. The structure and molecularweight of these compounds are not disclosed. For the purpose ofincreasing the density of open porous structures, the image receivinglayer contains colloidal oxides such as colloidal silicon dioxide orsilicon dioxide modified with aluminum oxide without disclosingadvantageous quantity ratios.

Finally, DE 34 33 528 C2 proposes a recording material for inkjetprinting with a carrier containing, at least in the surface region, awater-soluble metal salt of a metal with an ionic valence of 2 to 4 anda cationic organic material chosen from alkylamine salts, quaternaryammonium salts, polyamines and basic latices from the group of polyaminelatices and alkylammonium latices. Examples of polyamines mentionedtherein include polyethylamine epichlorohydrin. However, the text doesnot contain further indications of its especially suitablerepresentatives nor does it refer to any particular arrangements ofspecific representatives of polyethylamine epichlorohydrin. The textalso does not indicate any teaching of advantageous characteristics ofthe pigments to be employed, e.g., with respect to particle size.

For a long time, pigment-based recording inks were rarely used in placeof inks based on organic dyes, particularly acidic azo dyes. Problemswith this type of recording ink have to do with the low light fastnessof the organic dyes along with the problem of fading and discolorationof the printed images, which could be solved heretofore onlyunsatisfactorily by means of UV absorbers in the recording inks and bymeans of color stabilizers in the inkjet recording materials. Thepigment-based recording inks that have been used in the meantime havesubstantially greater light stability than the organic dye-based inksmentioned above. However, the pigment-based recording inks have theproblem of ink bleeding, by which is meant that directly adjoiningprinted patterns of different colors run into one another directly afterthe printing process. The recording material according to the inventionwas developed for use with pigment-based recording inks andsignificantly reduces the problem of ink bleeding.

There are basically two different processes of droplet generation ininkjet printing. The continuous process provides an inkjet which isejected under pressure from a nozzle and which separates into very smalldroplets at a certain distance from the nozzle due to surface tension.The droplets are electrically charged and, by means of deflecting plateswhich are electronically controlled by the electrical field, aresubsequently either deflected into a collecting vessel or placed on therecording material depending on the printed image to be generated.

In the discontinuous drop-on-demand process, as it is called, the inkdroplets, depending on the printed image to be generated, are generatedand ejected from a nozzle only when an image point is to be generated onthe recording material. One type of drop-on-demand printer uses thepiezoelectric effect in which an electrically controlled piezo-elementseparates an ink droplet from the reservoir of recording ink and ejectsthis droplet from a nozzle. In contrast, bubblejet printers use anelectrically controlled heating element which allows very smallquantities of aqueous ink to form in a steam bubble. The resulting steampressure ejects the droplet.

SUMMARY OF THE INVENTION

The invention is directed to recording materials which can be used inboth discontinuous processes.

It is the object of the present invention to provide an economicalrecording material for inkjet printing processes which is particularlysuitable for printing upon with pigment-based recording inks indiscontinuous processes. The novel recording material ensuresoutstanding fixing of the applied inks and thus reduces ink bleeding.The orientation of the novel recording material toward pigmented inksenables an extensive light fastness of the applied printed images.

Since pigmented inks are preferably used in poster printing and sincethe posters produced in this way, e.g., advertising posters, are exposedto direct sunlight, a novel recording material characterized by highstability with respect to any tendency toward yellowing is preferablyprovided. The recording material should also ensure that the appliedprinted images exhibit at least acceptable resistance to smudging whenwet.

In contrast to the teachings previously disclosed in this technicalfield, the inventors recognized as the result of numerous productiontests and comparison tests that the above-stated object is met by arecording material for the inkjet printing process with a substrate andan ink receiving layer which is applied on at least one side of thesubstrate, the ink receiving layer comprising an inorganic pigment andan ink fixative which includes at least two substances, the firstsubstance being a polyamine epichlorohydrin and the second substancebeing a polyvalent metal salt, wherein the first substance is amedium-molecular, branched polyamine epichlorohydrin condensationproduct; the ratio of the first substance to the second substance isbetween 3:1 and 16:1; the pigment makes up at least 80 percent by weightwith a D₅₀ particle size (Malvem) ranging from 4 μm inclusive to 12 μminclusive; and the ratio of ink fixative to pigment ranges from 1:2inclusive to 1:6 inclusive.

Within the meaning of the present invention, the polyamineepichlorohydrin condensation product is defined as medium-molecularinsofar as it has a viscosity in a range from 15 m Pa*s to 50 m Pa*s asa 10-percent aqueous solution. The above-mentioned viscosity isdetermined using Brookfield (spindle 1 at 100 rpm and 25° C.).

The invention is based on the choice of the polyamine epichlorohydrincondensation product as first substance of the ink fixative containingat least two substances. It is essential to the invention that thepolyamine epichlorohydrin condensation product is in medium-molecular,branched form. Other configuration types of polyamine epichlorohydrincondensation product prove to be unsuitable for various reasons; forexample, the use of a low-molecular, non-branched polyamineepichlorohydrin condensation product is to be avoided because recordingmaterials containing them have too strong an odor due to the free amine.

As second substance, the ink fixative must comprise a polyvalent metalsalt in order to meet the object upon which the invention is based.

Based on comparisons carried out in the framework of extensive series oftests, the inventors recognized that good ink fixing with minimum inkbleeding behavior and acceptable resistance to smudging when wet occursonly with a ratio (oven dry) of the first substance to the secondsubstance of between 3:1 and 16:1. A preferable ratio (oven dry) of thefirst substance to the second substance is in the range between 6:1 and14:1 with excellent ink fixing and greatly reduced ink bleeding behavioraccompanied by particularly convincing resistance to smudging when wet.

The second substance of the ink fixative is particularly magnesiumchloride, aluminum chloride and particularly preferably calcium chlorideas representatives of the polyvalent metal salts.

The ratio, according to the invention, of ink fixative to pigment rangesfrom 1:2 to 1:6 with respect to the percentage by weight of pigment andink fixative in the ink receiving layer. This ratio is limited on theone hand by sharply decreasing resistance to wet smudging which is notacceptable in larger amounts of ink fixative beyond an inkfixative-to-pigment ratio of 1:2 and, on the other hand, by anincreasingly worsening ink bleeding behavior which is no longerconvincing in smaller quantities of ink fixative beyond an inkfixative-to-pigment ratio of 1:6.

In accordance with the findings of the series of tests upon which thepresent invention is based, the inventors recognized that particularlygood characteristics of the novel recording material result when the inkfixative-to-pigment ratio ranges from 1:3 inclusive to 1:5.5 inclusivewith respect to the percentage by weight of pigment and ink fixative inthe ink receiving layer; the percentage by weight again refers to all ofthe ink fixative and pigment incorporated in the ink fixative layer.

However, it was completely surprising to the inventors that the objectupon which the present invention is based could be fully andconvincingly met when, simultaneous with the above-mentioned features,the inorganic pigment makes up at least 80 percent by weight with aparticle size ranging from 4 μm inclusive to 12 μm inclusive and, in aparticularly advantageous manner, from 5 μm to 12 μm inclusive as D₅₀value (Malvern—that is, determined in accordance with the specificationsof the pigment producer using the Malvern method). A range between 6 μmand 12 μm as D₅₀ value (Malvern) is particularly preferred.

It has been shown in comparison tests that the ink bleeding behavior issignificantly worse when poly-diallyldimethylammonium chloride(poly-DADMAC) is used as ink fixative alone or exclusively combined withpolyvalent metal salt. The use of polyethylene amine orpoly-dicyanodiamide is excluded due to an increased tendency towardyellowing in the recording materials having these cationic polymers.

According to the invention, the ink fixative of the recording materialaccording to the invention comprises the polyamine epichlorohydrincondensation product to be used as first substance and the secondsubstance comprising a polyvalent metal salt. However, the ink fixativecan also contain one or more additional compounds conventional for inkfixative such as poly-diallyldimethylammonium chloride, cationicpolyacrylamides, cationic polyacrylates, polyvinylamines,polyethyleneimines and polydicyanodiamides or a low-molecular,non-branched polyamine epichlorohydrin condensation product insofar asit makes up an amount not exceeding 30 percent by weight, particularly10 percent by weight, with respect to the total quantity of inkfixative.

It has proven advantageous that the proportion by weight of ink fixativein the ink receiving layer preferably ranges from 5 percent by weight to20 percent by weight; this total proportion can be selected tendingtoward the lower limit when applying ink receiving layers with high massper unit area within the above range.

The proportion of pigment in the ink receiving layer of the recordingmaterial according to the invention ranges from 30 to 70 percent byweight. For this purpose, aluminum hydroxide, silica gel and silicicacid have proven successful in particular. The last three pigments canbe modified by aluminum or aluminum oxide, or not modified.

The inorganic pigments mentioned previously can make up the pigmentproportion of the ink receiving layer of the recording material,according to the invention, individually or in combination with oneanother and/or in combination with other inorganic pigments.

The ink receiving layer of the recording material according to theinvention comprises a proportion of binder and co-binder ranging from 10to 55 percent by weight. Aqueous polymer dispersions of ethylene-vinylacetate and particularly styrene-butadiene latex, polyacrylates andsolutions of partially or completely saponified polyvinyl alcohol usedalone or in combination have proven particularly favorable.

Aside from the ingredients discussed above, the ink receiving layer ofthe recording material according to the invention can also containadditional components such as caustic soda, optical brightening agentsand defoaming agents without being limited thereto. They are added asneeded and constitute up to 5 percent by weight of the ink receivinglayer, the individual proportions taken together accounting for 100percent by weight.

In order to satisfy the spectrum of requirements in a convincing manner,the selected mass per unit area of the ink receiving layer should not betoo small because otherwise the resistance to smudging when wetdecreases too sharply and ink bleeding cannot be reduced to a sufficientdegree. The mass per unit area of the ink receiving layer is limited atthe top primarily for economical reasons.

It has been shown in numerous tests that it is advantageous to form theink receiving layer in two layers positioned one on top of the other.According to a preferred embodiment, a bottom layer communicates withthe substrate or with a preparation layer applied to the substrate, anda top layer is applied to the bottom layer. Especially good results canbe achieved when the first layer has a mass per unit area between 4 and12 g/m², preferably between 6 and 8 g/m², and the second layer has amass per unit area between 2 and 10 g/m², preferably between 4 and 6g/m². The same teachings apply for both layers with respect to theselection of components substantial to the invention and the ratio ofthese components relative to one another, particularly also in theirpreferred embodiment forms. The two layers also have the same auxiliarycomponents corresponding to the disclosures indicated herein.

When the ink receiving layer is formed with only one layer, therecommended mass per unit area of this layer is between 4 and 18 g/m²,particularly ranging from 5 to 10 g/m² and especially particularly from7 to 9 g/m².

The solids contents and viscosities of the coating compounds for formingan individual layer or, in the preferred embodiment form, two layers ofthe ink receiving layer according to the invention are adapted to thecoating method to be used.

In principle, the invention is not limited with respect to the coatingmechanisms that are used for applying the ink receiving layer. Levelingor equalizing coating methods such as doctor rolls or blades and contourcoating methods such as nozzle coaters or preferably curtain coaters andair brushes are possible in particular, although the invention is notlimited thereto. If the ink receiving layer is applied in two layers, itis particularly advantageous to apply the first layer with a levelingcoating method such as doctor rolls or blades—in the preferredembodiment form, on-line inside the paper machine—and to apply thesecond layer with a contour coating method, preferably with a curtaincoater or an air brush which can be integrated inside a separate coatingmachine.

At least one preparation layer preferably having a mass per unit arearanging from 0.5 to 2 g/m² is preferably arranged between the substrateand the individual layer, or first layer in the preferred embodimentform, of the ink receiving layer. The preparation layer can be formed asa single starch coat.

In a particularly preferred embodiment form, the recording materialaccording to the invention comprises a back coating on the side locatedopposite from the side with the ink receiving layer; this back coatingcan be formed as an ink receiving layer or as a single starch coat. As astarch coat, it serves to ensure good grip so that there will be notransporting problems in the inkjet printers. Improved printability canalso be achieved particularly in offset printing processes by means of asingle starch coat. The starch coat formed as a back coating preferablyhas a mass per unit area ranging from 0.1 to 2.0 g/m².

The invention further comprises a method for recording using thediscontinuous inkjet printing process with a pigment-based recording inkand with a recording material according to the invention which can beformed in one of the preferred embodiment forms described above. In thenovel method, the recording material according to the invention can beprinted upon by drop-on-demand printers which use either thepiezoelectric effect or which, as bubblejet printers, use anelectrically controlled heating element to eject very small inkdroplets.

The values specified in the description and patent claims for mass perunit area, percent by weight, parts by weight and component ratios referto O.D. weight, i.e., oven-dry parts by weight, unless otherwise noted.The abbreviation “A.D.” stands for air dry and, when used, means thatthe components thus characterized are described in their commerciallyavailable as -shipped form.

The following examples and comparison examples will illustrate theinvention more fully.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Production of a Substrate

A paper web of bleached, milled hardwood and softwood kraft pulps isproduced as a substrate on a fourdrinier paper machine with the additionof the usual quantities of conventional additives with a mass per unitarea of 82 g/m². A starch preparation of 0.8 g/m² is applied to thefront side of the paper web and a starch preparation of 0.4 g/m² isapplied to the back of the paper web.

Basic Recipe 1 for the Production of Coating Compounds for an InkReceiving Layer for Examples 1, 5, 6 and 7 According to the Inventionand Comparison Examples 2, 3, 4, 8 and 9

The following components referring to a total of 500 parts per weight(A.D.) are added to a vessel accompanied by continuous stirring:

% Solids Component (O.D.) Content [%] % (A.D.) Water^(*4) — —279.6/278.6/270.4 Caustic soda [10-percent] 0.3 10 3.0 Pigment^(*1) 58.8100 58.8 Optical brightening agent 3.0 50 6.0 Mixture of binder(PVAI^(*2), fully saponified) 24.8 20 124.0 and co-binder (EVAC^(*3))first substance ink fixative 11.8 Ex. 1: Polyamine epichlorohydrinconden- 48 24.6 sation product-medium-molecular, branched Comparison Ex.2: Poly-DADMAC 36 32.8 Calcium chloride 1.2 30 4.0 Defoaming agent 0.110 1.0 Total 100 20 500 ^(*1)Pigment mixture of two silica gels notmodified by aluminum, particle size at 80 percent by weight: 8 μm; at 20percent by weight: 10 μm; D₅₀ value (Malvern) ^(*2)Polyvinyl alcohol^(*3)Ethylene vinyl acetate ^(*4)Example 1/Example 2/Comparison Example3

As ink fixative in the coating compound in Example 1, a composition ofmedium-molecular, branched polyamine epichlorohydrin condensationproduct and calcium chloride is used in a ratio of polyamineepichlorohydrin condensation product to calcium chloride of 9.8:1.

In contrast to Example 1, the coating compound according to ComparisonExample 2, with all other components remaining the same, haspoly-diallyldimethylammonium chloride instead of polyamineepichlorohydrin condensation product. To form the single-layer inkreceiving layers, the coating compounds are applied at 8.5 g/m² to thefront side of the paper web whose production was described above.Samples of Example 1 and Comparison Example 2 were made in this way.

Using an inkjet printer, HP DesignJet 2500 CP by Hewlett Packard, and UVinks by the same manufacturer, a control printing is applied to bothsamples in order to analyze the ink bleeding behavior (printing mode:normal, no color matching; printer driver: heavy coated paper). Based onvisual inspection, the ink bleeding behavior of the samples of Example 1is judged to be good, while the ink bleeding behavior of the samples ofComparison 2 is judged to be poor.

For the following Examples 5, 6 and 7 and Comparison Example 3, 4, 8 and9, coating compounds are produced according to the oven dry proportionsin Example 1 and, corresponding to Example 1, are applied to a paperweb, whose production was described above, with a mass per unit areaaccording to Table 1. Compared to Example 1, the ratio of themedium-molecular branched polyamine epichlorohydrin condensation productto calcium chloride varies.

Again, using an inkjet printer, HP DesignJet 2500 CP by Hewlett Packard(printing mode: normal, no color matching; printer driver: heavy coatedpaper), and UV inks by the same manufacturer, a control printing isapplied to the samples to analyze the ink bleeding behavior. The inkbleeding behavior of the samples is assessed visually.

In order to analyze the resistance to smudging when wet, the printedimages by which the ink bleeding behavior of the samples was judgedpreviously are sprinkled with water. After a waiting period of 2seconds, a finger is repeatedly rubbed with uniform pressure over theprinted image. The printed image should smudge as little as possible,ideally not at all.

In Table 1, examples according to the invention are indicated by “EB”and comparison examples are indicated by “VB”. The determinedmeasurements and findings are given in Table 1:

TABLE 1 Ratio of amine Viscosity of epichlorohydrin coating Mass/unitcondensation compound area of ink Resistance product to [Brookfieldreceiving Ink to calcium (spindle 2/50 layer bleeding smudging Examplechloride rpm/25° C.)] [g/m²] behavior when wet 3 VB 1:5 744 8.4 goodpoor 4 VB 1.5:1  >2000 7.9 good poor 5 EB 3:1 360 8.4 good satisfactory6 EB 9:1 336 8.2 good good 7 EB 12.5:1   352 8.2 good good 8 VB 20:1 368 8.3 unsatisfactory good 9 VB 100:1  368 8.4 poor good (no calciumchloride)Basic Recipe 2 for the Production of Coating Compounds for an InkReceiving Layer for Examples 11, 14, 17 and 20 According to theInvention and Comparison Examples 10, 12, 13, 15, 16, 18, 19 and 21 to24:

The following components referring to a total of 500 parts per weight(A.D.) are added to a vessel while continuously stirring:

% Solids Component (O.D.) Content [%] % (A.D.) Water — — 279.6 Causticsoda [10-percent] 0.3 10 3.0 Pigment 58.8 100 58.8 Optical brighteningagent 3.0 50 6.0 Mixture of binder (PVAI^(*1), fully saponified) 24.8 20124.0 and co-binder (EVAC^(*2)) Polyamine epichlorohydrin condensation11.8 50 23.6 product Calcium chloride 1.2 30 4.0 Defoaming agent 0.1 101.0 Total 100 20 500 ^(*1)Polyvinyl alcohol ^(*2)Ethylene vinyl acetatepolymer

Silica gel which is not modified by aluminum and has a pore volume of1.2 ml/g is used as pigment with the following average particle sizesand specific inner surface area:

Pigment Pigment Pigment Pigment Pigment 1 2 3 4 5 Particle size [μm] 46.5 8 10 15 D₅₀ (Malvern) Specific inner surface 290 390 290 390 175[m²/g]

The ink receiving layer provided in the examples for basic recipe 2 is acomposition containing as first substance a polyamine epichlorohydrincondensation product with the following difference:

Ink fixative A: medium-molecular, non-branched (36.5 m Pa * s) Inkfixative B: medium-molecular, branched (35 m Pa * s) Ink fixative C:high-molecular, non-branched (91 m Pa * s)

Further, the ink fixative contains calcium chloride as second substancewhich is used in a ratio of polyamine epichlorohydrin condensationproduct to calcium chloride of 9.8:1.

The numbers appearing in parentheses in the preceding list of inkfixatives show the viscosity of the polyamine epichlorohydrincondensation product as 10-percent aqueous solution as measured withBrookfield (spindle 1 at 100 rpm and 25° C.)

Examples 11, 14, 17, 20 and Comparison Examples 10, 12, 13, 15, 16, 18,19 and 21 to 24

Fifteen samples of different recording materials for the inkjet printingprocess were produced. Fifteen different coating compounds correspondingto the basic recipe given above were prepared. Each of the five pigments1, 2, 3, 4 and 5 introduced were combined with each of the ink fixativesA, B or C together with calcium chloride. The coating compounds wereapplied to the paper web, whose production was described above, to formthe ink receiving layers. Again, using an inkjet printer, HP DesignJet2500 CP by Hewlett Packard (printing mode: normal, no color matching;printer driver: heavy coated paper), and UV inks by the samemanufacturer, a control printing is applied to the 20 samples to examinethe ink bleeding behavior. The ink bleeding behavior of the samples isassessed visually.

In Table 2, examples according to the invention are indicated by “EB”and comparison examples are indicated by “VB”. The determinedmeasurements and findings are given in Table 2:

TABLE 2 Viscosity of Mass/unit area coating compound of ink Ink Ink[Brookfield (spindle receiving layer bleeding Example Pigment fixative2/50 rpm/25° C.)] [g/m²] behavior 10 VB 1 A >800 8.4 poor 11 EB 1 B 5368.2 barely good 12 VB 1 C >800 8.6 poor 13 VB 2 A 408 7.8 poor 14 EB 2 B344 8.8 good 15 VB 2 C >800 8.7 poor 16 VB 3 A 352 7.8 unsatisfactory 17EB 3 B 264 8.3 good 18 VB 3 C >800 8.8 poor 19 VB 4 A 672 8.0 poor 20 EB4 B 440 8.1 good 21 VB 4 C >800 8.1 poor 22 VB 5 A 208 8.3 very poor 23VB 5 B 144 8.0 poor 24 VB 5 C 720 8.1 poor

Based on the basic recipe 2 and the ink receiving layer componentsaccording to Example 17, the ink fixative-to-pigment ratio varies. Thesamples produced in this way are analyzed with respect to ink bleedingbehavior and resistance to smudging when wet of the printed imagesapplied to them.

In order to analyze the resistance to smudging when wet, the printedimages which were previously used for judging the ink bleeding behaviorof the samples were sprinkled with water. After a waiting period of 2seconds, a finger is repeatedly rubbed with uniform pressure over theprinted image. The printed image should smudge as little as possible,ideally not at all.

Examples 17, 26, 27 and Comparison Examples 25, 28

For Comparison Example 25 and Example 26 according to the invention, asmaller amount of ink fixative and, therefore, a greater amount of allother components are added to a vessel while continuously stirring inorder to reduce the proportion of ink fixative—referring to 500 partsper weight (A.D.) of the basic recipe 2. For Example 27 according to theinvention and Comparison Example 28, a greater amount of ink fixativeand, therefore, a smaller amount of all other components are added to avessel while continuously stirring in order to increase the proportionof ink fixative referring to 500 parts per weight (A.D.) of basic recipe2. The subsequent production of the samples and the respectiveapplication of a control print are carried out in accordance with thepreceding description.

Table 3 shows the adjusted ink fixative-to-pigment ratios and thevisually assessed ink bleeding behavior of the samples and theresistance to smudging when wet of the applied printed images. Examplesaccording to the invention are indicated by “EB” and comparison examplesare indicated by “VB”.

TABLE 3 Resistance to Ink fixative-to- Ink bleeding smudging Examplepigment ratios behavior when wet 25 VB  1:10 poor very good 26 VB 1:5good good 17 EB   1:4.53 good good (see also TABLE 2) 27 EB  1:3.3 goodsatisfactory 28 VB  1:1.5 good poor

The examples according to the invention illustrate particularly clearlythat the recording material according to the invention convincinglysucceeds in providing an economical recording material for inkjetprinting processes that ensures excellent fixing of the applied inksparticularly when printing with pigment-based recording inks andaccordingly reduces ink bleeding, which is not the case in thecomparison examples. Further, the examples according to the inventionshow that the novel recording material ensures an acceptable resistanceto smudging when wet in the applied printed images, which the comparisonexamples are not capable of providing.

1. A recording material for an inkjet printing process comprising asubstrate and an ink receiving layer applied on at least one side of thesubstrate, the ink receiving layer containing an inorganic pigment andan ink fixative comprising at least first and second substances, thefirst substance being a polyamine epichlorohydrin and the secondsubstance being a polyvalent metal salt, wherein the first substance isa branched polyamine epichlorohydrin condensation product that has aviscosity in a range from 15 m Pa*s to 50 m Pa*s as a 10-percent aqueoussolution as determined by using a Brookfield spindle 1 at 100 rpm and25° C., the ratio of the first substance to the second substance isbetween 3:1 and 16:1, at least 80 percent by weight of the pigment ismade of particles having a D₅₀ particle size (Malvern) ranging from 4 μminclusive to 12 μm inclusive, and the ratio of ink fixative to pigmentranges from 1:2 inclusive to 1:6 inclusive.
 2. The recording material ofclaim 1, wherein the second substance is a polyvalent metal saltselected from a group including magnesium chloride, aluminum chlorideand calcium chloride.
 3. The recording material of claim 1,characterized in that the ratio of the first substance to the secondsubstance is between 6:1 and 14:1.
 4. The recording material of claim 1,wherein at least 80 percent by weight of the pigment is made ofparticles with a D₅₀ particle size (Malvern) ranging from 6 μm to 12 μm.5. The recording material of claim 1, wherein the pigment is selectedfrom the group including aluminum hydroxide, silicic acid and silicagel.
 6. The recording material of claim 1, wherein the ratio of inkfixative to pigment ranges from 1:3 inclusive to 1:5.5 inclusive.
 7. Therecording material of claim 1, wherein the ink receiving layer includesat least one binder selected from the group including polyvinyl alcohol,styrene-butadiene latex, polyacrylates and polymer dispersions ofethylene-vinyl acetate.
 8. The recording material of claim 1, furthercomprising at least one preparation layer arranged between the substrateand the ink receiving layer.
 9. The recording material of claim 1,wherein the ink receiving layer includes two layers positioned one ontop of the other.
 10. A method for recording using a discontinuousinkjet printing process comprising the step of applying a pigment-basedrecording ink using a discontinuous inkjet printing process onto arecording material according to claim 1.